This disclosure generally relates to non-destructive inspection equipment and methods, and relates more particularly to methods and apparatus for inspecting elongated members, such as stiffeners, made of composite material.
Non-destructive inspection of structures involves thoroughly examining a structure without harming the structure or requiring its significant disassembly. Non-destructive inspection is commonly used in the aircraft industry to inspect aircraft structures for any type of anomaly in the structure. Non-destructive inspection is also used in the initial fabrication of the aircraft's structural components. It is used to assure that a part was fabricated correctly and to ensure that no foreign material was embedded within the part. Inspection may be performed during manufacturing of a structure and/or after a structure has been put in service
Non-destructive inspection (NDI) may be performed on stiffened composite parts of an aircraft. Composite parts such as fuselages and wings are frequently stiffened using elongated composite members called “stringers”. These stiffeners may be made of a composite material such as carbon fiber-reinforced plastic (CFRP). As used herein, the term “elongated composite members” includes but is not limited to composite stiffeners used in the construction of fuselages and wings of aircraft, such as wing blade stiffeners and wing vent stiffeners.
More specifically, the quality of a stiffener can be determined non-destructively by ultrasonic testing. A stiffener can be inspected ultrasonically by a probe, including one or more shoes that hold respective ultrasonic transducer arrays, that is moved incrementally along the length of the stiffener. As the probe is being moved, the transducer arrays may operate in pulse/echo mode to generate pulsed ultrasonic waves, which propagate into the stiffener. Reflected ultrasonic waves are returned to and detected by the ultrasonic transducer arrays to provide data indicative of the presence of anomalies in the stiffener. Data acquired by the ultrasonic transducer arrays is typically processed by a computer system, and the processed data may be presented to a user via a computer monitor. A data acquisition device and data handling software may be used for collection and display of inspection data, such as displaying the data on a computer monitor as an image representation of the structure under inspection, such as a stringer, supplemented with corresponding color and/or graphical data of the inspection to permit examination by a qualified inspector.
Automated inspection systems typically employ a manipulator (e.g., overhead gantry, multi-axis scanner, or robot) that scans an NDI end effector along the part being inspected. For single-sided inspection methods, such as pulse echo ultrasonic inspection, a single-arm robotic device having multiple degrees of freedom may be used to position and move an NDI end effector, such as a pulse echo ultrasonic inspection device, attached to the end of the robot arm.
Some stiffeners incorporated in aircraft wings are inspected in large immersion tanks, which can have an impact on overall manufacturing throughput and on the required factory floor space for the inspection system. In a feed-through immersion system, stiffeners may move through the inspection probes by keeping the probes relatively stationary inside a small immersion tank. This process requires the system to be twice as long as the part because the part must be fed into one side of the immersion tank and then exit the other side.
It would be advantageous to provide a single-pass NDI system designed so that the part can remain stationary during inspection, thereby reducing the inspection time required and the amount of factory space occupied by the inspection station.